The invention relates to a two-piece joining device for sheet pile retaining walls that consists of two interlocking strip-shaped joining elements.
Sheet pile retaining walls such as sheet pilings or foundations are e.g. constructed of pipes that are to be pile-driven into the ground, a joining element being welded to each pipe and interlocking with a corresponding joining element of an adjacent pipe.
Customary joining elements are so-called LARSSEN's hooks; cf. e.g. FR 2648493.
So-called ball-and-socket joining elements are in particular used in the USA. The first joining element (ball joining element) is affixed, as a rule, welded, to a first pipe with a base and comprises a neck strip projecting away from the base and the pipe and an adjoining button strip; the second joining element is welded to the adjacent pipe with its base and comprises two hook strips projecting away from its base and the pipe, which define between them a hollow space and embrace the button strip of the first joining element that is inserted into the hollow space upon the pile-driving of the pipes in such a way that it is held in the hollow space. An example of such joining elements is shown in the German Utility Model 200 17 445; cf. FIGS. 1 and 3 thereof.
Upon the pile-driving of the piles with the welded joining elements, considerable tensile forces partly occur between the pipes, which are i.a. caused by the non-homogeneity of the ground. The tensile forces may partly be that high so that, in particular in the case of conventional Larssen's hooks, but also in the case of ball-and socket connections, the interlocking joining elements are bent up and detached from each other. In the case of ball-and-socket connections which, as compared with LARSSEN's hooks, are capable of absorbing higher tensile forces the hook strips of the second joining element may be bent up by the button strip of the first joining element to such an extent that the button strip of the first joining element jumps out of the hook strips of the second joining element so that the connection between the pipes is interrupted there. This is of particular disadvantage if a liquid-tight connection is to be established between the pipes. If this jumping out of the two joining elements is noticed at all, the pile-driving must be repeated; if the jumping out is not noticed, which is frequently the case, the wall constructed in this fashion is no longer liquid-tight, which entails considerable subsequent work to eliminate this damage.
There is, of course, the possibility of designing the joining elements as a whole in a more stable fashion, e.g. with thicker wall thicknesses; however, since the price of these joining elements is substantially determined by weight of the material, i.e. usually the weight of steel, this, as a rule, is refrained from.